@HaruLin , Thank you for your reply.
Indeed it might be just one entry for Unkown Artist, but I can not allow such error in my collection. I chose to complete all empty albumartist fields. Since I started my collection in the 90’s it took me a long time to fix this.
After filling all fields and no longer pushing the re-index button, I found out that new albums have been added overnight. I guess I’ve been not patient enough! I might have been spoiled by Plex which has plenty settings.
